A standalone Unix environment that runs in a browser tab — shell, git, npm, node, vi, C compiler, SQLite, Python, and Claude Code. One HTML file. No server.

Live: shiro.computer Docs: shiro.computer/docs About: shiro.computer/about Examples: examples/

• 220+ commands — ls, grep, awk, sed, find, curl, diff, xargs, tar, wc, sort, uniq, factor, base32, numfmt, dos2unix...
• Persistent filesystem — IndexedDB-backed. Files survive reloads.
• Git — isomorphic-git: init, add, commit, diff, log, clone, push
• npm — Real tarballs from registry.npmjs.org. require() resolves node_modules.
• Node.js runtime — Run .js files. CommonJS and ES module transforms.
• C compiler — xcc compiles C to WebAssembly, runs via WASI
• SQLite — sql.js WASM. Persistent databases in IndexedDB.
• Python — Pyodide WASM. pip installs packages.
• Lua, jq, esbuild — Lazy-loaded WASM runtimes, cached on first use
• x86-64 emulator — Runs real Linux ELF binaries (musl-static) via instruction-level emulation. ~135 instructions, ~60 syscalls, SSE2, JIT block cache.
• tmux — Terminal multiplexer with split panes, sessions, detach/attach
• SSH/SCP over WebRTC — Peer-to-peer shell sessions and file transfer between browser tabs
• Compression — bzip2, xz, zstd with full tar integration (-j/-J/--zstd)
• Init system — systemctl services, cron scheduling, journalctl logs
• Claude Code — The real @anthropic-ai/claude-code CLI runs inside the browser
• Virtual servers — serve hosts apps, page interacts with them
• Windowed terminals — spawn opens commands in their own window with interactive REPL
• Template palette — 13 educational templates across 4 categories (Web, Languages, Packages, Tools) including WASM package manager, x86 Linux binaries, full-stack Express+SQLite, and cross-language data pipelines
• One HTML file — ~420 KB gzipped. Deploy anywhere. Works offline.

# Shell basics
echo "hello" | sed 's/hello/world/' | wc -c
mkdir -p src && echo 'console.log("hi")' > src/app.js
find . -name "*.js" | grep -l "console"

# Git (isomorphic-git)
git init && git add . && git commit -m "initial"
git log --oneline

# npm (real tarballs from registry.npmjs.org)
npm install lodash prettier
node -e "console.log(require('lodash').uniq([1,1,2]))"

# C compiler → WebAssembly
echo '#include <stdio.h>\nint main(){printf("hello\\n");}' > hi.c
cc hi.c -o hi && ./hi

# SQLite
sqlite3 app.db "CREATE TABLE users(name TEXT); INSERT INTO users VALUES('alice');"
sqlite3 app.db "SELECT * FROM users;"

# x86-64 emulator (runs real Linux binaries)
./hello              # Auto-detect ELF binary, run in emulator
x86 run ./hello      # Explicit execution
x86 debug ./hello    # Step-through with register dumps

# Serve and interact with web apps
serve /tmp/myapp 3000
page :3000 click "#button"
page :3000 text "body"

# Heredocs
cat > /tmp/hello.html << 'EOF'
<h1>Hello World</h1>
EOF
serve /tmp 3000

# Windowed terminals
spawn                    # Open a blank interactive terminal window
spawn node server.js     # Run command in a window, then drop to REPL
title "My App"           # Set the window title

# Claude Code (runs inside the browser)
claude -p "create a todo app with localStorage"

The real @anthropic-ai/claude-code CLI runs inside Shiro's Node.js runtime shim. The tools Claude Code relies on — file reads, edits, grep, glob, bash — are shimmed to use the virtual filesystem. Both print mode (claude -p "...") and interactive mode (claude) work. API calls route through a CORS proxy to Anthropic's API.

An outer Claude Code instance can also control Shiro remotely via MCP tools over WebRTC. Run remote start in Shiro, then connect with the shiro-mcp package.

~50 shimmed Node.js modules. Core modules (fs, path, buffer, events, process, crypto, os, url, util, child_process) are fully functional. See the full compatibility table.

npm install
npm run dev          # Dev server at localhost:5173
npm run build        # Build to dist/
npm run deploy       # Build + deploy to shiro.computer

MIT

Note: Experimental. Claude Code runs with --dangerously-skip-permissions (all tool calls auto-approved). API requests transit a CORS proxy. Don't use with sensitive data.